Field of the Invention
The present invention relates to a light source unit, a control method thereof, and a projection-type display apparatus.
Description of the Related Art
There is proposed for a projection-type display apparatus such as a liquid crystal projector, a method of irradiating a fluorescent member (phosphor) with light from a light source (hereinafter, referred to as a “solid-state light source”) that includes a semiconductor such as a light-emitting diode (LED) and a laser and of using light having a converted wavelength. Excitation light is blue, and fluorescence includes a wavelength band of a plurality of color beams corresponding to three primary colors of light. The light source can be configured to emit light in a wide wavelength band by synthesizing the excitation light and the fluorescence, and the color of a projected image can be adjusted by applying this light source to the projection-type display apparatus.
For example, Japanese Patent Laid-open No. (“JP”) 2012-108486 discloses a configuration in which excitation light is guided onto a fluorescent member by using a polarizing beam splitter (“PBS”). The PBS selectively transmits and reflects light having the wavelength of the excitation light, and reflects light having the wavelength of fluorescence. Part of the excitation light incident on the fluorescent member is dispersively reflected because its polarization is disordered. This disordered polarization due to the irradiation on the fluorescent member is exploited to reflect part of the excitation light at the PBS and to synthesize the excitation light with the fluorescence so as to output both lights. JP 2012-189938 discloses a method of mixing a dispersive filler with a device including a fluorescent member and of outputting both fluorescence and excitation light when the excitation light passes through the fluorescent member device.
The method disclosed in JP 2012-108486 uniquely determines the ratio of the excitation light and the fluorescence by the transmission-reflection characteristic of the PBS or the area ratio of fluorescent member region distributed over a fluorescent member device. The method disclosed in JP 2012-189938 determines the ratio of the excitation light and the fluorescence by the mixing amount of the filler. Therefore, none of the prior art references can change the ratio of the excitation light and the fluorescence after the light source unit is produced.